332 



REVISION OF THE MONAXONID SPONGES, 11. 



interstices, the diameter of which varies from about 150 to 400/x, 

 are separated by relatively narrow lines or by relatively broad. 

 The interior of the sponge is traversed by abundant canals, of 



which the largest measure 4 mm. in 

 diameter; and, in consequence of 

 this, its structural appearance, as 

 shown on a cut surface, somewhat 

 resembles that of well aerated bread. 

 The consistency is firm and moder- 

 ately tough. The colour in spirit is 

 greyish-brown within, and yellowish- 

 grey on the surface. 



The main skeleton(Pl. xvii., fig. 6) 

 is halichondroid, consisting of a 

 dense, irregular, ill-defined mesh- 

 work of spicule-bundles; fibres, in 

 the proper sense of the term, can 

 scarcely be said to be present, and 

 even the bundles as a rule are not 

 very distinct as such. Frequently 

 the dispositiot) of the spicule-bun- 

 dles is such as to produce a some- 

 what lattice-like pattern; but even 

 so, the pattern is much confused. 

 For the most part, the bundles are 

 multispicular, and the meshes of the 

 network are very much less in width 

 Aviorphmopsis mega- ^han the length of the spicules. The 



rrhaphea. a, Principal spicules, -, , i^- i -• /ii i. a 



, ,, , . ^ . , dermal reticulation (the meshes ot 



a', Abnormal forms (very rare) 



of the preceding, with acces- ^^^^^i^h, as already stated, measure 

 sory actines near one extremi- in diameter from 150 to 400 /x) is 

 ty. 6, Dermal styli. formed by coarse fibres, varying 



from 130 to upwards of 280 /x in stoutness, composed of oxea 

 similar to those of the main skeleton. Supported upon these 

 fibres are closely-crowded short styli, which stand perpendicu- 

 larly to the surface with their apices directed outwards. Styli 

 similar to these also occur scattered sparsely through the interior. 



